Profiled bar, and vehicle spring produced therefrom

ABSTRACT

A vehicle spring for a spring system, includes a spring body ( 20 ) and is produced, in particular rolled, from a profiled bar ( 1 ) made of a flat steel bar, in particular spring steel, in a hot deformation process. The profiled bar ( 1 ) or the spring body ( 20 ) has at least one material recess ( 6 ) which is provided over the length of the profiled bar or the spring body at least in some regions. The cross-sectional shape of the profiled bar ( 1 ) can be the same over the entire length of the profiled bar, whereas the cross-sectional shape in the spring body ( 20 ) can vary over the length of the spring body.

The invention relates to a profiled bar that is made of flat-bar steel,in particular spring steel, for producing a hot-deformed, in particularrolled, vehicle spring, as well as a method for producing such aprofiled bar.

In addition, the invention relates to a vehicle spring with an elongatedspring body, which is produced, in particular rolled, in a hot-deformedmanner from a profiled bar, as well as a method for producing such avehicle spring.

Moreover, the invention relates to a spring system for a vehicle.

As used in the invention, vehicle spring can be defined as an air spring(bar spring), a parabolic spring, a leaf spring, in particular asingle-leaf parabolic spring and a multi-leaf parabolic spring, whichare produced from flat-bar steel.

Within the framework of the invention, vehicle springs are hot-deformed,in particular rolled, from flat-bar steel, preferably spring steel, attemperatures of approximately 800 to 1200° C. In the case ofhot-deformed vehicle springs that consist of flat-bar steel, the vehiclesprings receive their springy function from the material, i.e., thevehicle spring has an inherent springy action because of the startingmaterial. According to EN 10089, 3.1, spring steel is described asfollows: “Materials, which because of their properties in theheat-treated state are especially suitable for the production of springyparts of all types. The springiness of steel is based on its elasticdeformability, because of which it can be heavily loaded within aspecific range without undergoing a permanent change in shape after theload is removed . . . .”

Spring systems are known, in which carriers are cast (e.g., as disclosedin DE 10 2008 061 190) or welded (e.g., as disclosed in WO 2003/064192);these carriers are not springs in the conventional sense. Such carrierscannot—in contrast to the hot-deformable steel—be hot-deformed butrather can be processed only at significantly higher temperatures. Incontrast to this, e.g., flat-bar steel that is made of spring steel isalmost unweldable. Moreover, the cast or welded carriers do not gain aprimarily springy action because of their material properties in thestate of use in a spring system. Based on the material properties, thesecarriers form a rigid system per se. The springy action of this systemis first achieved by the special connection of the carrier, in mostcases by a lug that is incorporated in the carrier or a carrier supportthat is made of rubber.

When forging is done with forged steel (e.g., as disclosed inWO2009/014423), no spring is produced by rolling a profiled bar that ismade of flat-bar steel.

Vehicle springs are used in motor vehicles, in particular in utilityvehicles or trailers (towed vehicles). The requirements of the motorvehicle industry are characterized, on the one hand, by the reduction ofthe weight of individual components. On the other hand, due toincreasing engine output, the requirements are characterized by the factthat individual components undergo increasingly high mechanicalstresses. In this case, it is problematic in hot-deformed vehiclesprings that are made of flat-bar steel that the weight of the vehiclespring cannot be easily reduced, since the vehicle spring, in particularof the spring body, must—because of its springy function—withstand otherstresses as cast or welded products. To date, weight of a vehicle springwas reduced in that—starting from the same starting material forproducing the vehicle spring—the geometry of the finished vehicle springwas changed to increase the surface tension in such a way that thevehicle spring could be constructed in a more compact manner.

The object of the invention is to make available a vehicle spring of theabove-mentioned type, whose weight in comparison to a conventionalvehicle spring is reduced, whereby the inherent springy function of thespring body continues to be ensured and the mechanical load capacity isnot impaired. In certain applications, a more compact design can also beachieved.

According to the invention, it is provided that the profiled bar has atleast one material recess, which is provided over its length at least insome places. Thus, the weight of the vehicle spring produced from theprofiled bar can be reduced by the geometry of the starting product thatis used up to approximately 30% or more, whereby the force absorptionand the springy action of the spring body are not impaired. Also, morecompact vehicle springs can thus be produced at a consistent weight.

Within the framework of the invention, the profiled bar is preferablyproduced from a spring steel according to DIN EN 10089.

In an especially preferred embodiment, the material recess extends overthe entire length of the profiled bar. In addition, it is preferred thatthe cross-sectional shape of the profiled bar is the same over itslength, i.e., that the cross-sectional shape of the profiled bar doesnot change over its length.

Within the framework of the invention, the profiled bar has a top, abottom and two narrow sides, whereby at least one material recess isprovided preferably in at least one narrow side. As an alternative or inaddition to this, at least one material recess can be provided in thebottom.

In particular, it is preferred when the material recess is punched outas a depression in width b and/or in height h of the profiled bar in atleast one central area of the bottom or the narrow side. The profiledbar has a longitudinal axis, a transverse axis that runs crosswise tothe longitudinal axis, which transverse axis preferably corresponds tothe neutral fiber, as well as an axis that runs at right angles to thetransverse axis from the bottom to the top, whereby in an especiallyadvantageous embodiment, a material recess runs in the area of thetransverse axis and/or in the area of the axis, and/or whereby thecross-sectional shape is symmetric to the axis.

In an especially preferred embodiment of the invention, the profiled barin the cross-section corresponds to an I-profile. Within the frameworkof the invention, other profile shapes can also be provided, such as,e.g., U- or T-profiles.

According to the invention, it is furthermore provided that the profiledbar is produced by material being displaced in the longitudinaldirection of the profiled bar.

It is provided according to the invention, moreover, that thehot-deformed spring body, which has a springy action in the installedstate, has at least one material recess, which is provided over itslength at least in some places.

In one embodiment of the invention, the material recess can extend overthe entire length of the vehicle spring. In other embodiments of theinvention, it can be provided that the length of the material recess is1 to 99% of the length of the vehicle spring, in particular 10 to 90% or20 to 80% or 40 to 40% or approximately 50% of the profiled bar.

In an especially preferred embodiment of the invention, the spring bodycorresponds at least in sections to an I-profile in cross-section.Within the framework of the invention, other profile shapes can also beprovided, such as, e.g., U- or T-profiles.

Since rolling processes take place during the production of vehiclesprings, it is preferred within the framework of the invention when thecross-sectional shape of the spring body changes over its length, inparticular when the width of the material recess changes over the lengthof the material recess. Thus, the width of the material recess can bematched to the optimal shape of the finished spring, whereby areas withdifferent bending strength can also be achieved.

The depth of the material recess in the profiled bar and/or in thespring body can increase or decrease continuously or intermittently overthe width of the material recess—considered in cross-section. The depthof the material recess can increase and/or decrease continuously, e.g.,straight or arc-shaped, or can increase and/or decrease, e.g., in steps,whereby the depth of the material recess remains the same in sections.Also, the depth of the material recess can first increase, and thenremain the same or decrease, and then increase again, or the depth canonly increase.

As material recesses, one or more grooves (material recesses) thatoptionally run parallel to one another can also be provided.

A vehicle spring is produced from an elongated profiled bar according tothe invention in such a way that the profiled bar with at least onematerial recess, which is provided over the length of the profiled barat least in some places, is hot-deformed, in particular rolled. Inparticular, it can be provided that as starting material for the hotdeformation, a profiled bar with at least one material recess is used,whose cross-sectional shape is the same over its entire length, wherebyduring hot deformation, the width of the material recess changes to avarying extent over the length of the spring body.

Within the framework of the invention, material recess is defined as asavings of material, i.e., that material otherwise present in the areaof the material recess is replaced by the material recess, or thatotherwise present material is not present. In particular, within theframework of the invention, material recess can be defined as materialin the area of the material recess being displaced in the longitudinaldirection of the profiled bar. In contrast to this, e.g., finned leafsprings do not have any material recess, since here, the material is not“displaced” in longitudinal direction but rather in the directionperpendicular to the transverse axis of the profiled bar. Also, e.g.,imprints in a profiled bar or in a vehicle spring do not mean a materialrecess, since in the case of imprints, material is not displaced overthe (preferably entire) longitudinal direction of the profiled bar orthe spring body.

During the production of the profiled bar according to the invention,material is displaced in the longitudinal direction of the profiled bar.This can take place in that the profiled bar is guided along a form thathas at least one protrusion, for example a nose, whose cross-sectionalshape represents a negative image of the desired cross-sectional shapeof the material recess in the finished profiled bar.

For example, the production process of a vehicle spring can besummarized as follows:

A profiled bar, in particular a flat-bar steel, with a material recesswith a consistent cross-sectional shape over its entire length, is cutto the desired length. Within the framework of the invention, preferablya flat-bar steel according to EN 10092 or BS 970-2 and a spring steelaccording to EN 10089 or EN 10083 are used as starting material;however, other hot-deformable steels can also be used. Within theframework of the invention, depending on the country/region,standardized spring steels or heat-treatable steels can also be used.For the subsequent hot forming, the profiled bar is brought to atemperature of approximately 800 to 1200° C. The profiled bar that iscut to length is rolled horizontally or vertically at this temperature,and the ends are processed accordingly depending on the desired vehiclespring. For rolling, the profiled bar is heated on one side, run betweenan open pair of rollers and then moved between the latter one or moretimes in the longitudinal direction. In this processing process, the gapbetween the rollers can be varied so that the desired shape of theprofiled bar is set. When the profiled bar is rolled, the width of thematerial recess can thus also be changed in a varying manner over thelength of the profiled bar by exerting varying pressures. Then, theprofiled bar is heated on the opposite side, and a renewed rollingprocess is performed.

Depending on the desired vehicle spring, in particular when multiplesprings are to be arranged over one another in the state of use(multi-layer springs), a center hole, a blind hole or other depressionsfor a spring screw or other positive elements can be introduced. Theprofiled bar can receive one or two lugs in an additional step. Therolled profiled bar that is heated again or is still at the necessarytemperature can then optionally run through one or more pressingstations for final processing, after which a rolling process can beperformed. The rolling of the ends to form lugs also takes place attemperatures from approximately 800 to 1,200° C. In additional steps,the spring (at approximately 900° C.) can be bent and then heat-treated.

Depending on the type of vehicle spring, both ends can have a lug. Oneend can also have a rolled or molded-on lug, e.g., introduced into thespring body; conversely, the other end is essentially flat. In thelast-mentioned embodiments, the profiled bar can be angled or bent inparticular in the area of the flat end. In another embodiment, two endscan also be essentially flat and optionally slightly bent (without alug).

Depending on the type of vehicle spring, the processing steps can bechanged. Within the framework of the invention, the profiled bar canalso be heated initially to a specific processing temperature, wherebyin the case of the subsequent processing steps, no further heating isnecessary.

Features of the cross-sectional shape or shapes of the profiled bar, inparticular the shape of the material recess over the height of theprofiled bar, can also be present in the spring body. Features of thecross-sectional shape or shapes of the spring body, in particular theshape of the material recess over the height of the spring body, canalso be present in the profiled bar.

Preferred and advantageous embodiments of the invention follow from thedescription below with reference to the attached drawings, in whichpreferred embodiments are depicted.

Here:

FIGS. 1 to 5 show known cross-sectional shapes of profiled bars forvehicle springs that are made of hot-deformable steel;

FIGS. 6 to 11 show embodiments of profiled bars for a vehicle springaccording to the invention in cross-section;

FIG. 12 shows a first embodiment of a bar spring according to theinvention with a rolled lug;

FIG. 13 shows a second embodiment of a bar spring according to theinvention with a lug introduced into the spring body; and

FIG. 14 shows an embodiment of a parabolic spring according to theinvention.

In FIGS. 1 to 5, cross-sectional shapes of profiled bars 1 that are madeof flat-bar steel and that are known to date are depicted, namely anatural-edged profile (FIG. 1), a profile with semi-circular narrowsides (FIG. 2), a profile with rounded edges (FIG. 3) and a basket-archprofile (British Standard) (FIG. 4). FIG. 5 shows in cross-section ahot-deformable profiled bar 1 for finned leaf springs.

The hot-deformable profiled bars 1 depicted in FIGS. 1 to 3 correspondto DIN EN 10092-1. FIG. 4 shows a hot-deformable profiled bar 1 that ismade of flat-bar steel with a cross-sectional shape according to BritishStandard BS 970-2:1988 b. The hot-deformable profiled bar 1 depicted inFIG. 5 corresponds to DIN EN 10092-2. The profiled bars 1 have a top 2,a bottom 3 and two narrow sides 4, 5. Furthermore, in FIGS. 1 to 4, thewidth b, the height h, and the transverse axis z (this also correspondsto the neutral fiber defined with respect to the bending stress) of theprofiled bars 1 as well as radii of curvature r are indicated. Accordingto FIGS. 1 to 4, the profiled bars 1 have no material recess over theirlength. Also, the profiled bar 1 depicted in FIG. 5 has no materialrecess over its length, since in the finned area, all material ispresent, and the material is also not displaced in the longitudinaldirection.

In contrast to the known profiled bars 1, a profiled bar 1 according tothe invention has at least one material recess 6. Thus, the weight of ahot-rolled vehicle spring can be reduced by the starting material,whereby the force absorption and the springy action of the vehiclespring are not impaired.

By way of example, a profiled bar 1 (in particular that is made offlat-bar steel) is depicted in FIG. 6, which bar (starting from a knownprofiled bar 1 according to FIG. 3) in its two narrow sides 3, 4 in eachcase has a material recess 6 with a width B and a depth T. The materialthat is otherwise present on the narrow sides 4, 5 (as in, e.g., FIG. 3)is displaced in the profiled bar 1 according to FIG. 6 along itslongitudinal direction and is no longer present in the profiled bar 1.In the embodiment depicted in FIG. 6 and in FIG. 7, the profiled bar 1has an I-profile with a material recess 6 that is arc-shaped incross-section. The depth T of the material recess 6 continuouslyincreases first over its width B and then continuously decreases again.

A difference between the embodiments depicted in FIGS. 6 and 7 is thatthe bottom 3 of the profiled bar 1 according to FIG. 7 is less wide thanits top 2.

In the embodiment depicted in FIG. 8, the profiled bar 1 has a U-profilethat is open downward with a material recess 6 that is arc-shaped incross-section, i.e., the material recess 6 is provided in the bottom 3.

In the embodiment depicted in FIG. 9, the profiled bar 1 has anessentially trapezoidal cross-sectional shape with rounded edges. Thematerial recess 6 runs from the upper area of the profiled bar 1 in astraight line to the bottom 3, whereby the depth T of the materialrecess 6 continuously increases over its width B. The material recess 6is provided in two narrow sides 4, 5 as well as in the bottom 3.

In the embodiment depicted in FIG. 10, the profiled bar 1 has aT-profile with a material recess 6 that is wave-shaped in cross-section.Also, in this embodiment, the depth T of the material recess 6 increasescontinuously over its width in the direction toward the bottom 3.

In the embodiment depicted in FIG. 11, material recesses 6 are providedin the two narrow sides 4, 5, which recesses are shaped similar to thosein FIG. 9. Moreover, a material recess 6 is provided in the bottom 3,which recess is shaped similar to that in FIG. 8.

A feature that all depicted embodiments of profiled bars 1 according tothe invention have in common is that the profiled bar 1 has a transverseaxis z that runs crosswise to its longitudinal axis (the latter cancorrespond to the neutral fiber) as well as an axis V that runs at rightangles to the transverse axis z and that the cross-sectional shape issymmetric to the axis V. Furthermore, all embodiments shown have incommon the fact that the material recess 6, relative to an imaginarycross-sectional surface that is formed by the width b and the height hof the profiled bar 1 (depicted in hatching in FIGS. 6 to 11), extendsinto the profiled bar 1. Relative to the imaginary cross-sectionalsurface, formed by the width b and the height h of the profiled bar 1,edge areas can be defined by the height h and the width b in the area ofthe corners (these can also be rounded corners), as well as centralareas. Within the framework of the invention, the material recess 6 is adepression of width b and/or height h of the profiled bar 1 in at leastone central area. In particular, it can be provided that at least onematerial recess 6 runs in the area and in particular along thetransverse axis z and/or in the area and in particular along the axis(V).

In the depicted profiled bars 1, the material recess 6 extends over theentire length of the profiled bar 1, whereby the cross-sectional shapeof the profiled bar 1 does not change over its entire length.

If a vehicle spring with a spring body 20 can be produced from theprofiled bar 1, one or more features of the material recess 6 containedin the profiled bar 1 can also be present in the spring body 20. Also,the shape of the material recess in the spring body 20 (for example,width B of the material recess 6 that continuously or intermittentlyincreases and/or decreases over the height of the spring body 20 or, forexample, depth T of the material recess 6 that continuously orintermittently increases and/or decreases over the width B of thematerial recess 6) can already be present in the profiled bar 1. In thefinished vehicle spring, mixed shapes of possible material recesses 6 orcross-sectional shapes can also be present. In the finished vehiclespring, the material recess 6 cannot run over the entire length of thespring body 20, whereby the cross-sectional shape of the material recess6 in the spring body can change.

In FIG. 12, an embodiment of a bar spring according to the inventionwith a spring body 20 that is made of a hot-deformed profiled bar 1 isdepicted. The bar spring has a rolled lug 8 on one of its longitudinalends 7. The other longitudinal end 9 is angled and has two boreholes 10,which are used for mounting, e.g., an air spring bellows.

The spring body 20 has a through material recess 6 over a major part ofits length on the two narrow sides 4, 5 and is vigorously rolled to avarying extent over its length. Because of the rolling, the width B ofthe material recess 6 changes over the length of the spring body 20. Thedepth T of the material recess 6 continuously increases and decreasesagain in this embodiment. In the embodiment depicted in FIG. 12, thespring body 20 has an I-profile, whereby the material recess 6 over thelength of the spring body 20 has a depth T that is consistent for themost part.

In FIG. 13, another embodiment of a bar spring according to theinvention that consists of a hot-deformed profiled bar 1 is depicted. Onone of its longitudinal ends 7, the bar spring has a molded-on lug 11.The other longitudinal end 9 is angled.

The spring body 20 has a through material recess 6 over its entirelength on the two narrow sides 4, 5, and is vigorously rolled to avarying extent over its length. Because of the rolling, the width B ofthe material recess 6 changes over the length of the spring body 20. Thedepth T of the material recess 6 increases and decreases to a varyingextent in this embodiment. In the area of the longitudinal end 7, inwhich area the lug 11 is molded-on, the spring body 20 has an I-shapedprofile according to the profiled bar 1 of FIG. 6. Its cross-sectionalshape changes over the length of the spring body 20; e.g., in thecentral section of the profiled bar 1, the depth T of the materialrecess 6 essentially increases and decreases in stages.

In FIG. 14, an embodiment of a parabolic spring according to theinvention that consists of a hot-deformed profiled bar 1 is depicted.The parabolic spring has a rolled lug 8 on both ends. The spring body 20has an I-profile viewed in cross-section, whereby the width of thematerial recess 6 over a portion of the length of the spring body 20increases or decreases and remains the same over a part of the length ofthe spring body 20.

In the FIGS. 12 to 14 (as also in particular in FIGS. 6 and 7), thespring body 20 (or profiled bar 1) has a neutral fiber, whereby thematerial recess 6 is a depression of width b of the profiled bar 1 overits height h in the area of and along the neutral fiber. This preferredembodiment can also hold true in the case of cross-sectional shapes thatare not depicted.

In summary, an embodiment of the invention can be depicted as follows:

A vehicle spring for a spring system with a spring body 20 is producedin a hot-deformed manner, in particular rolled, from a profiled bar 1that is made of flat-bar steel, in particular spring steel. The profiledbar 1 or the spring body 20 has at least one material recess 6, which isprovided at least in some places over its length. The cross-sectionalshape of the profiled bar 1 can be the same over its entire length;conversely, the cross-sectional shape in the spring body 20 can changeover its length.

1-26. (canceled)
 27. A profiled bar that is made of flat-bar, springsteel for producing a hot-deformed, rolled, vehicle spring having anelongated spring body, the profiled bar having a longitudinal axis, atransverse axis (z) that runs crosswise to the longitudinal axis andthat corresponds to the neutral fiber, and an axis (v) that runs atright angles to the transverse axis (z) from the bottom to the top ofthe profiled bar, the profiled bar also having a cross sectionperpendicular to the longitudinal axis thereof, the cross sectiondefining a trapezoid at least in some places over the length of, theprofiled bar.
 28. The profiled bar of claim 27 wherein the cross sectionhas a top side, a bottom side, a first narrow side and a second narrowside, each side defining a flat segment, each of the first and secondnarrow sides extending between the top and bottom sides, and wherein atleast one material recess having a depth which increases continuouslyover the width thereof is provided in the first narrow side, and atleast in some places over the length of, the profiled bar.
 29. Theprofiled bar of claim 28 wherein a second material recess having a depthwhich increases continuously over the width thereof is provided in thesecond narrow side, and at least in some places over the length of theprofiled bar.
 30. The profiled bar of claim 28 wherein the at least onematerial recess overlaps the transverse axis (z).
 31. The profiled barof claim 28 wherein the flat segment of the first narrow side runscontinuously from a location below the neutral fiber to a location abovethe neutral fiber.
 32. The profiled bar of claim 28 wherein the flatsegment of the second narrow side runs continuously from a locationbelow the neutral fiber to a location above the neutral fiber.
 33. Theprofiled bar of claim 28 wherein the flat segment of the first narrowside extends from a location adjacent the bottom side to a locationadjacent the top side.
 34. The profiled bar of claim 28 wherein the flatsegment of the second narrow side extends from a location adjacent thebottom side to a location adjacent the top side.
 35. The profiled bar ofclaim 28 wherein the flat segments of the top and bottom sides areparallel to one another.
 36. The profiled bar of claim 28 wherein theflat segment of the bottom side extends over the entire length of theprofiled bar.
 37. The profiled bar of claim 28 wherein the at least onematerial recess extends over the entire length of the profiled bar. 38.The profiled bar of claim 27 wherein the cross-section of the profiledbar is the same over the length of the profiled bar.
 39. The profiledbar of claim 27 wherein the cross-section of the profiled bar issymmetric to the axis (V).
 40. A vehicle spring with an elongated springbody, which is produced in a rolled, hot-deformed manner from a profiledbar, the elongated spring body having a longitudinal axis, a transverseaxis (z) that runs crosswise to the longitudinal axis and thatcorresponds to the neutral fiber, and an axis (v) that runs at rightangles to the transverse axis (z) from the bottom to the top of theelongated spring body, the elongated spring body also having a crosssection perpendicular to the longitudinal axis thereof, the crosssection defining a trapezoid at least in some places over the length ofthe elongated spring body.
 41. The vehicle spring according to claim 40,wherein the cross section has a top side, a bottom side, a first narrowside and a second narrow side, each side defining a flat segment, eachof the first and second narrow sides extending between the top andbottom sides, and wherein at least one material recess having a depthwhich increases continuously over the width thereof is provided in thefirst narrow side, and at least in some places over the length of theelongated spring body.
 42. The vehicle spring of claim 41 wherein asecond material recess having a depth which increases continuously overthe width thereof is provided in the second narrow side, and at least insome places over the length of the elongated spring body.
 43. Thevehicle spring of claim 41 wherein the at least one material recessoverlaps the transverse axis (z) of the elongated spring body.
 44. Thevehicle spring of claim 41 wherein the flat segment of the first narrowside runs continuously from a location below the neutral fiber to alocation above the neutral fiber.
 45. The vehicle spring of claim 41wherein the flat segment of the second narrow side runs continuouslyfrom a location below the neutral fiber to a location above the neutralfiber.
 46. The vehicle spring of claim 41 wherein the flat segment ofthe first narrow side extends from a location adjacent the bottom sideto a location adjacent the top side.
 47. The vehicle spring of claim 41wherein the flat segment of the second narrow side extends from alocation adjacent the bottom side to a location adjacent the top side.48. The vehicle spring of claim 41 wherein the flat segments of the topand bottom sides are parallel to one another.
 49. The vehicle spring ofclaim 41 wherein the flat segment of the bottom side extends over theentire length of the elongated spring body.
 50. The vehicle spring ofclaim 41 wherein the at least one material recess extends over theentire length of the elongated spring body.
 51. The vehicle spring ofclaim 41 wherein the length of the at least one material recess is 20 to80% of the length of the elongated spring body.
 52. The vehicle springof claim 41 wherein the length of the at least one material recess is50% or more of the length of the elongated spring body.
 53. The vehiclespring of claim 41 wherein the cross-section of the elongated springbody is symmetric to the axis (V).
 54. The vehicle spring of claim 41wherein the elongated spring body has two longitudinal ends and a rolledlug or molded-on lug on at least one longitudinal end.
 55. The vehiclespring of claim 40 wherein the vehicle spring is a parabolic spring withthe elongated spring body having a parabolic portion and the at least insome places over the length of the elongated spring body includes theparabolic portion.
 56. The vehicle spring of claim 41 wherein thevehicle spring is a parabolic spring with the elongated spring bodyhaving a parabolic portion within which the at least one material recessis positioned.